JP2011231419A - Steel cord for reinforcing rubber article and tire using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a steel cord for reinforcing rubber article, improved in durability as compared with a conventional one, without increasing weight thereof, when applied to a tire, and to provide a tire using the steel cord.SOLUTION: The steel corm 10 for reinforcing a rubber article has a multi-twisted structure obtained by twisting a plurality of strands made by twisting a plurality of filaments. A bundle in which a plurality of wrapping filaments 3 is aligned is wound around the steel cord for reinforcing the rubber article. The strand is preferably twisted together into a layer twisted structure composed of a core and a sheath of at least one layer, and the filaments are preferably twisted together into the layer twisted structure.

Description

  TECHNICAL FIELD The present invention relates to a steel cord for reinforcing rubber articles (hereinafter, also simply referred to as “steel cord”) and a tire using the same, and more specifically, when applied to a tire, it has a higher durability than a conventional one without increasing its weight. The present invention relates to an improved steel cord for reinforcing rubber articles and a tire using the same.

  In the case of steel radial tires for construction vehicles, they are used under heavy loads on rough uneven surfaces, etc., so the steel cord that is the skeleton member requires extremely high strength and durability. . In order to ensure high strength and durability corresponding to the increase in size of such tires, the steel cord has a double twist structure.

  The double twist structure is a structure in which a plurality of strands obtained by twisting a plurality of filament wires are further twisted, and a wrapping filament is wrapped on the outermost side. The role of the wrapping filament is mainly to prevent scattering to improve workability in processing. In addition, it has a role of maintaining durability as a rubber-cord composite by maintaining the cord shape against bending and compression input.

  As a technique for improving a steel cord having a wrapping filament, for example, Patent Document 1 discloses a technique for improving compression durability with a wrapping filament. Specifically, a wrapping filament is wound around a steel cord body made of a plurality of filaments in a spiral shape with an amplitude in a direction orthogonal to the cord radial direction. Therefore, when tension is applied to the wrapping filament, the wrapping filament is deformed in the direction of increasing the wavelength. Thereby, the tension | tensile_strength concerning a wrapping filament is relieve | moderated and the fracture | rupture of a wrapping filament is suppressed.

  In addition to this, many techniques for preventing a fretting phenomenon in which a wrapping filament damages a cord body are disclosed. For example, Patent Document 2 discloses a steel cord wrapped with a stranded wire formed by twisting steel filaments. Further, Patent Document 3 discloses a steel cord wrapped with a steel filament having a spiral shape. Further, Patent Document 4 discloses a steel cord wrapped with a steel filament having a flat cross section. Furthermore, Patent Literature 5 discloses a steel cord including a wrapping filament wound around a spiral in the same direction as the twist direction of the coaxial layer around the outermost coaxial layer. In addition to these, Patent Document 6 discloses a steel cord having a longer pitch of the wrapping filament while maintaining the restraint of the steel cord by the wrapping filament, and Patent Document 7 discloses a plurality of wrapping filaments in the same direction. A steel cord wound at the same pitch and at substantially equal intervals is disclosed.

JP 2004-323979 A JP 11-43877 A Japanese Utility Model Publication No. 5-27094 JP-A-8-27681 JP-A-6-17384 Japanese Patent Laid-Open No. 9-310289 JP 2004-68213 A

  According to the techniques described in Patent Documents 1 to 7, it has been shown that the strength and durability of a steel cord having a wrapping filament can be improved. However, in recent years, there has been an increasing demand for durability on tires, and it has become difficult to say that the techniques described in Patent Documents 1 to 7 are sufficiently satisfactory. This is the current situation.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a steel cord for reinforcing rubber articles and a tire using the same, which has improved durability as compared with the related art without increasing the weight when applied to a tire.

  In order to solve the above-mentioned problems, the present inventor has earnestly studied a steel cord having a double twist structure, and has obtained the following knowledge. That is, when a local bending or compression input is applied to a steel cord having a multi-strand structure forming a rubber-steel cord composite, a birdcage is a unit of a strand in which a plurality of filaments are twisted together. It was found that a strong action to spread like a shape occurs from inside the steel cord. As a result of further diligent studies based on this knowledge, when the shape of the steel cord is held with the wrapping filament, first, the wrapping filament is fatigued and fractured due to a large input concentration from the strand. As a result, it was found that the steel cord, which is no longer restricted by the wrapping filament, has a large deformation of the strand, and the failure proceeds to breakage of the entire steel cord. As a result of further intensive studies based on the above findings, the present inventors have found that the above problems can be solved by suppressing fatigue fracture of the wrapping filament at the initial stage of failure, and have completed the present invention.

That is, the steel cord for reinforcing rubber articles according to the present invention is a steel cord for reinforcing rubber articles having a double twist structure in which a plurality of strands formed by twisting a plurality of filaments are twisted together.
A bundle of a plurality of wrapping filaments is wound around the outer circumference of the steel cord for reinforcing rubber articles.

In the steel cord for reinforcing rubber articles according to the present invention, it is preferable that the strand is twisted in a layer twist structure including a core and at least one sheath. Moreover, it is preferable that the said filament is twisted together in a layer twist structure. Further, the wire diameter d of the wrapping filament and the cord diameter D of the steel cord excluding the wrapping filament are expressed by the following relational expression (1):
4 ≦ d / D × 100 (%) ≦ 7 (1)
It is preferable to satisfy the relationship represented by: Furthermore, the total cross-sectional area A of the wrapping filament and the total cross-sectional area B of the filament constituting the outermost layer sheath strand are expressed by the following relational expression (2):
1 ≦ A / B × 100 (%) ≦ 8 (2)
It is preferable to satisfy the relationship represented by:

  The tire of the present invention is characterized by using the steel cord for reinforcing rubber articles of the present invention as a reinforcing material.

  ADVANTAGE OF THE INVENTION According to this invention, when it applied to a tire, it became possible to provide the steel cord for rubber article reinforcement which improved durability conventionally, and a tire using the same, without increasing a weight.

It is a schematic sectional drawing of the steel cord of the (7x (3 + 9 + 15) +2) structure which concerns on one embodiment of this invention (Example 1). 6 is a schematic cross-sectional view of a steel cord having a (7 × (3 + 9 + 15) +6) structure according to Example 2. FIG. 6 is a schematic cross-sectional view of a steel cord having a (3 × (3 + 9 + 15) + 9 × (3 + 9 + 15) +3) structure according to Example 3. FIG. 6 is a schematic cross-sectional view of a steel cord having a (1 × (3 + 7) + 6 × (3 + 7) + 12 × (3 + 7) +9) structure according to Example 4. FIG. 6 is a schematic cross-sectional view of a steel cord having a (7 × (3 + 9 + 15) +1) structure according to Comparative Example 1. FIG. 6 is a schematic cross-sectional view of a steel cord having a (7 × (3 + 9 + 15) +2) structure according to Comparative Example 2. FIG. 6 is a schematic cross-sectional view of a steel cord having a (7 × (3 + 9 + 15) +1) structure according to Comparative Example 3. FIG. 10 is a schematic cross-sectional view of a steel cord having a (3 × (3 + 9 + 15) + 9 × (3 + 9 + 15) +1) structure according to Comparative Example 4. FIG. 10 is a schematic cross-sectional view of a steel cord having a (3 × (3 + 9 + 15) + 9 × (3 + 9 + 15) +1) structure according to Comparative Example 5. FIG. 10 is a schematic cross-sectional view of a steel cord having a (1 × (3 + 7) + 6 × (3 + 7) + 12 × (3 + 7) +1) structure according to Comparative Example 6. FIG. 10 is a schematic cross-sectional view of a steel cord having a (1 × (3 + 7) + 6 × (3 + 7) + 12 × (3 + 7) +1) structure according to Comparative Example 7. FIG. It is sectional drawing of the tire for construction vehicles which concerns on one embodiment of the tire of this invention.

DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.
The steel cord of the present invention has a multiple twist structure in which a plurality of strands formed by twisting a plurality of filaments, preferably 9 to 30, and preferably 6 to 20 strands are twisted. . When both the number of filaments and the number of strands are larger than the above range, in order to manufacture a cord having the same diameter, the number of manufacturing steps increases, and the manufacturing cost increases. On the other hand, when both the number of filaments and the number of strands are less than the above range, in order to produce a cord having the same diameter, the filament to be used must be made thick, and the fatigue resistance to bending becomes poor. FIG. 1 is a schematic cross-sectional view of a steel cord having a (7 × (3 + 9 + 15) +2) structure according to a preferred embodiment of the present invention. The illustrated steel cord 10 has seven strands formed by twisting 27 filaments into a (3 + 9 + 15) layer twist structure. This strand is twisted together in a layer twist structure having a core made of the core strand 1 and a single sheath made of the sheath strand 2.

  In the present invention, a bundle of a plurality of wrapping filaments 3, preferably 2 to 10, is wound around the outer periphery of the steel cord. Here, the bundle means a state in which the wrapping filaments 3 are localized and arranged on the outer periphery of the steel cord with an interval equal to or smaller than the filament diameter of the wrapping filament 3. When the wrapping filaments 3 are arranged in a form other than a bundle on the outer periphery of the steel cord, for example, when arranged evenly, the strong action that the strands try to spread from the inside of the steel cord 10 due to bending or compression input of the steel cord 10 Is received locally by one filament 3. Therefore, the maximum input applied to the filament 3 alone is larger than that of the bundle, and fatigue is easily caused. Therefore, in the present invention, by arranging a plurality of wrapping filaments 3 as bundles, the fatigue per wrapping filament 3 is reduced, the fatigue rupture of the wrapping filament 3 at the initial stage of failure is suppressed, and the double twist The durability of the steel cord 10 having the structure is improved.

  Further, by using a plurality of wrapping filaments 3, the cross-sectional area of the entire wrapping filament 3 is increased, the steel cord 10 is less likely to be fatigued and the tire durability is improved. As a method for increasing the cross-sectional area of the wrapping filament 3, it is conceivable to increase the diameter of the wrapping filament 3. However, as the diameter of the wrapping filament 3 increases, the diameter of the steel cord 10 itself also increases. Therefore, when a rubber-steel cord composite is manufactured using this steel cord 10, the amount of coating rubber used increases, and the tire The weight will increase. On the other hand, according to the present invention, it is not necessary to increase the diameter of the wrapping filament 3. Therefore, the diameter of the steel cord 10 itself does not increase, the amount of coating rubber used can be suppressed, and a thin and lightweight rubber-steel cord composite can be obtained.

  The steel cord 10 of the present invention has a double twisted structure in which a plurality of strands formed by twisting a plurality of filaments are further twisted, and a plurality of wrapping filaments 3 are arranged on the outer periphery of the steel cord. As long as the bundle is wound, the twist structure of the strand is not particularly limited, and may be a single twist structure or a layer twist structure. Moreover, there is no restriction | limiting in particular also about the twist structure of a filament, A single twist structure or a layer twist structure may be sufficient. Preferably, as shown in FIG. 1, the strand is twisted into a layer twist structure composed of a core and at least one layer of sheath, and the internal structure of the strand is formed by twisting a filament into a layer twist structure. And

In the present invention, the wire diameter d of the wrapping filament 3 and the cord diameter D of the steel cord 10 excluding the wrapping filament 3 are expressed by the following relational expression (1):
4 ≦ d / D × 100 (%) ≦ 7 (1)
It is preferable to satisfy the relationship represented by: When the value of d / D × 100 (%) is less than 4, the wrapping filament 3 becomes very thin, and the steel cord 10 and its rubber composite are likely to be disconnected, resulting in poor productivity. When the value of d / D × 100 (%) is larger than 7, the wrapping filament 3 becomes very thick and the thickness of the rubber composite needs to be increased, so that a sufficient light weight effect cannot be obtained. There is a case.

In the present invention, the total cross-sectional area A of the wrapping filament 3 and the total cross-sectional area B of the filament constituting the outermost sheath strand are expressed by the following relational expression (2):
1 ≦ A / B × 100 (%) ≦ 8 (2)
It is preferable to satisfy the relationship represented by: When the value of A / B × 100 (%) is less than 1, the total cross-sectional area of the wrapping filament 3 becomes very small, and the ability to constrain the shape of the steel cord 10 is insufficient, resulting in poor fatigue durability. There is a case. If the value of A / B × 100 (%) is larger than 8, the width of the bundle of the wrapping filaments 3 becomes too wide, and the rubber penetration into the steel cord 10 is uneven. Corrosion durability may deteriorate.

  The steel cord 10 of the present invention is not particularly limited with respect to the filament diameter, the cord diameter, the twist pitch, and the like to be used as long as the above-described conditions are satisfied in the steel cord having the double twist structure. It is possible to select as appropriate.

  The tire of the present invention uses the steel cord 10 of the present invention as a reinforcing material, and for example, a construction vehicle tire shown in FIG. 12 can be preferably cited. This construction vehicle tire has a carcass 21 made of a steel cord ply extending in a radial direction between a pair of bead cores 20 and at least two layers arranged on the outer side in the tire radial direction of the crown portion of the carcass 21 (illustrated example) 6 layers) and a tread 23 disposed on the outer side of the belt 22 in the tire radial direction.

  The tire of the present invention is obtained by applying the steel cord of the present invention to, for example, a carcass cord, a belt cord, or the like, thereby obtaining a tire having excellent durability without increasing the tire weight. it can. The tire of the present invention is not particularly limited except that the steel cord of the present invention is used as a reinforcing material, and can be appropriately configured according to a conventional method.

Hereinafter, the present invention will be described in more detail with reference to examples.
(Examples 1-4, Comparative Examples 1-7)
A steel cord having the following structure is manufactured, and the obtained steel cord is covered with rubber, and the obtained rubber-steel cord composite is used as a carcass ply. Prototyped 53 / 80R63). The details of the steel cord are summarized in Tables 1-3.

(Twisted structure)
Example 1: 7 × (3 + 9 + 15) × 0.24 mm + 2 × 0.25 mm
Comparative Example 1: 7 × (3 + 9 + 15) × 0.24 mm + 1 × 0.25 mm
Comparative Example 2: 7 × (3 + 9 + 15) × 0.24 mm + 2 × 0.25 mm
Comparative Example 3: 7 × (3 + 9 + 15) × 0.24 mm + 1 × 0.35 mm
Example 2: 7 × (3 + 9 + 15) × 0.24 mm + 6 × 0.15 mm
Example 3: 3 × (3 + 9 + 15) × 0.185 mm + 9 × (3 + 9 + 15) × 0.185 mm + 3 × 0.28 mm
Comparative Example 4: 3 × (3 + 9 + 15) × 0.185 mm + 9 × (3 + 9 + 15) × 0.185 mm + 1 × 0.28 mm
Comparative Example 5: 3 × (3 + 9 + 15) × 0.185 mm + 9 × (3 + 9 + 15) × 0.185 mm + 1 × 0.49 mm
Example 4: 1 × (3 × 0.24 mm + 7 × 0.35 mm) + 6 × (3 × 0.24 mm + 7 × 0.35 mm) + 12 × (3 × 0.24 mm + 7 × 0.35 mm) + 9 × 0.32 mm
Comparative Example 6: 1 × (3 × 0.24 mm + 7 × 0.35 mm) + 6 × (3 × 0.24 mm + 7 × 0.35 mm) + 12 × (3 × 0.24 mm + 7 × 0.35 mm) + 1 × 0.32 mm
Comparative Example 7: 1 × (3 × 0.24 mm + 7 × 0.35 mm) + 6 × (3 × 0.24 mm + 7 × 0.35 mm) + 12 × (3 × 0.24 mm + 7 × 0.35 mm) + 1 × 0.96 mm

(Twist pitch, twist direction)
A (Examples 1 and 2 and Comparative Examples 1 to 3)
7mm (Z) / 14mm (Z) / 21mm (Z) / 60mm (S) / 5mm (Z)
B (Example 3 and Comparative Examples 4 and 5)
6mm (Z) / 12mm (Z) / 18mm (Z) / 43mm (Z) / 70mm (Z) / 5mm (S)
C (Example 4 and Comparative Examples 6 and 7)
6.5mm (S) / 13mm (S) / 40mm (S) / 70mm (Z) / 8mm (S)

  A sample having a width of 10 cm, a length of 15 cm, and a thickness of 6 cm was cut out from the bead folded portion of the obtained tire with the second rim line position as the center. The compression fatigue resistance and lightness of the steel cord were evaluated using the obtained samples. The evaluation method is as follows.

<Compression fatigue>
An input of 6% compression strain, 5 Hz, 500,000 repetitions was applied to the obtained sample indoors, and the presence or absence of wrapping filaments after the test was observed. The case where the wrapping filament was not broken was marked with ◯, and the case where it was broken was marked with X. The obtained results are also shown in Tables 1-3.

<Lightweight>
The thickness of the rubber-steel cord composite was compared. As the index, the steel cord thickness (D + 2d) including the wrapping filament was calculated, and the lightness comparison index was obtained and displayed according to the following formula. A smaller value indicates a thinner and lighter member and better.
(Lightness comparison index) = (D + 2d) (mm) of steel cord subject to index calculation / (D + 2d) (mm) × 100 (%) of steel cord used as a reference
Here, in Examples 1 and 2 and Comparative Examples 1 to 3, Example 1 is used. In Examples 3 and 4 and 5, Example 3 is used. In Examples 4 and 6 and 7, Examples are used. 4 is the standard steel cord. The obtained results are also shown in Tables 1-3.

<Processability>
As a reference, as an evaluation of workability, the presence or absence of productivity problems was evaluated during tire preparation. ○ indicates good, and × indicates defects such as disconnection.

  From Tables 1 to 3 above, according to the present invention, it was confirmed that when applied to a tire, a steel cord for reinforcing a rubber article capable of improving durability without increasing the weight and a tire using the same can be obtained. It was.

1 Core Strand 2 Sheath Strand 3 Wrapping Filament 10 Steel Cord 20 Bead Core 21 Carcass 22 Belt 23 Tread

Claims (6)

In the steel cord for reinforcing rubber articles having a double twist structure formed by twisting a plurality of strands formed by twisting a plurality of filaments,
A steel cord for reinforcing rubber articles, wherein a bundle of a plurality of wrapping filaments is wound around the outer circumference of the steel cord for reinforcing rubber articles.   The steel cord for reinforcing rubber articles according to claim 1, wherein the strands are twisted together in a layer twist structure comprising a core and at least one sheath.   The steel cord for reinforcing rubber articles according to claim 1 or 2, wherein the filament is twisted into a layer twist structure. The wire diameter d of the wrapping filament and the cord diameter D of the steel cord excluding the wrapping filament are expressed by the following relational expression (1):
4 ≦ d / D × 100 (%) ≦ 7 (1)
The steel cord for reinforcing rubber articles according to any one of claims 1 to 3, satisfying a relationship represented by: The total cross-sectional area A of the wrapping filament and the total cross-sectional area B of the filament constituting the outermost sheath strand are expressed by the following relational expression (2):
1 ≦ A / B × 100 (%) ≦ 8 (2)
The steel cord for reinforcing rubber articles according to any one of claims 1 to 4, which satisfies a relationship represented by:   A tire using the steel cord for reinforcing rubber articles according to any one of claims 1 to 5 as a reinforcing material.

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